Can't Send Mail To AOL

Hi there,

I'm new to the forum and to using Zimbra. I installed Zimbra last week on Linux (the latest version for download) and have been configuring/setting it up ever since. The major problem I had was getting the IM to work.. but a post on this forum detailed the "zmprov" commands necessary to get that working. After a restart, almost everything seems to be running well. I have setup about ten accounts and all can send/receive to all domains EXCEPT aol.com. Every time an email has been attempted to goto aol.com, it comes up with deferred in the mail queue (admin panel) and the following error message:

host {removed} said: 421-: (dns:nr) 421 service not available (in reply to end of data command)

Gmail, Yahoo, Hotmail all work fine. I'm not a system administrator / network guy, rather a PHP developer (and have just been reading reading as much as possible so I could get Zimbra setup...), but I'm lost as to how to resolve the error above. I read the page listed, which says:

Reverse DNS lookup for your IP address is failing. AOL does require that all connecting Mail Transfer Agents have established reverse DNS.

Is AOL the only one that demands Reverse DNS lookup? How do I configure this and where?

For rDNS this would need to be configured by your ISP who control the network block. A more simple solution would be to use your ISPs mail server as a smart-relay which can be configured within the ZCS Admin GUI under MTA.

For rDNS this would need to be configured by your ISP who control the network block. A more simple solution would be to use your ISPs mail server as a smart-relay which can be configured within the ZCS Admin GUI under MTA.

Hmmm... interesting.. I will contact our hosting company. We have a dedicated server for zimbra.. so I have no idea who the ISP is.

Are you referring to changing the option : Web mail MTA Hostname? Currently this is set as zimbra.example.com.. I'm wondering if changing this to mail.example.com would work. The mail server (cPanel) used to be mail.example.com and sending emails to aol worked fine before.

For rDNS this would need to be configured by your ISP who control the network block. A more simple solution would be to use your ISPs mail server as a smart-relay which can be configured within the ZCS Admin GUI under MTA.

MX record.

Not only does AOL check your PTR record it will also check to see if your server's response to the HELO command is equal to the MX record. These are the same DNS checks Zimbra makes if you have that feature enabled.

More and more ISP's are going to be implementing these checks. My server stops at least 80% of spam before it even gets to the spam checks in Zimbra.